1. Field of the Invention
The present invention relates to connectors for flexible flat cables-printed circuits that possess flexibility, referred to as FPCs (Flexible Printed Circuits), FFCs (Flexible Flat Cables), and the like. In this specification, a flexible flat cable is generically referred to as an FPC. The present invention relates, in particular, to a connecting structure for an FPC connector and an FPC terminal.
2. Related Art
In electronic devices in recent years, flexible flat cables (FPCs) are used for connecting printed circuit boards and electronic component modules mounted in portable information devices typified by, for example, DVCs (Digital Video Cameras), DSCs (Digital Still Cameras), cell-phones, and PDAs (Personal Digital Assistants).
An FPC connector that is surface-mounted on a printed circuit board —what is called a surface-mounted FPC connector—is provided with: an insulating housing, on which an insertion area, into which an FPC is inserted, is formed, and a plurality of contacts mounted in parallel at a prescribed pitch on the housing. In order to make the FPC and the contacts touch, for example, a cover-housing that opens and closes is provided at the insertion area.
In raising the mounting density of FPC connectors that are surface-mounted on a printed circuit board, lowering of mounting height (lowering of profile) and reduction of mounting area are required, and progress is being made with multi-pin and narrow pitch contacts arrayed on these surface-mounted FPC connectors.
For this type of surface-mounted FPC connector, FPC connectors are being invented in which the mounting area on the printed circuit board is small, disconnection of a pair of FPCs from the FPC connector does not easily occur, and moreover, alignment with contacts is easy (for example, see Patent Document 1).
The FPC connector according to Patent Document 1 is formed of a socket-housing, an open-close cover-housing, and a plurality of contacts, and has a terminal socket into which terminals of the FPC pair are inserted. A first and a second FPC have, respectively, a first and a second flat terminal. The first flat terminal and the second flat terminal are disposed in parallel in the terminal socket, as a pair on the same plane, and the first FPC and the second FPC are connected to the FPC connector.
Moreover, first and second rectangular shaped protrusions are formed on the first and the second flat terminals. In a state in which the first and the second rectangular shaped protrusions are facing one another, when the first and the second flat terminals are inserted via the terminal socket into the socket-housing, the first and the second rectangular shaped protrusions make contact with a central protrusion provided in the socket-housing and are positioned with respect to insertion direction. When the cover-housing is closed, a disconnection-prevention protrusion provided in the cover-housing makes contact with the first and the second rectangular shaped protrusions, so that each of the first and the second FPCs does not easily disconnect from the FPC connector.
The pair of FPCs according to Patent Document 1 includes the first and the second rectangular shaped protrusions that can be disposed in a state in which they face one another; moreover, in the FPC connector according to Patent Document 1, the central protrusion for positioning the first and the second rectangular shaped protrusions, and a disconnection-prevention protrusion to prevent the pair of FPCs from detaching in a direction opposite to that of insertion, are provided. Accordingly, compared to cases in which two FPC connectors are disposed in parallel, with one FPC connector a central barrier is not necessary, and the mounting area of the FPC connector can be made small.
Furthermore, in a state with the cover-housing closed, the disconnection-prevention protrusion fits under a notch formed in the terminal socket, and by positioning the disconnection-prevention protrusion behind the first rectangular shaped protrusion or the second rectangular shaped protrusion, and the first rectangular shaped protrusion or the second rectangular shaped protrusion making contact with the disconnection-prevention protrusion, even if a force tending to disconnect the FPCs from the socket-housing acts on the first FPC or the second FPC, disconnection does not easily occur.
Furthermore, reverse insertion into a connector for multi-polar flat wires (referred to as FPC, below), can be assuredly prevented, and displacement between the terminal flat conductor and the contacts inside the connector does not occur, so that an FPC connector in which a stable connection can be assured is designed (for example, see Patent Document 2).
In the FPC connector according to Patent Document 2, a key groove open to the front end, asymmetrically positioned in a lateral direction, is formed on the terminal of the FPC, engaging concave portions are formed on left and right side ends of the terminal, and inside the connector connected to this FPC, contacts connected to conductive patterns on the terminal, and engaging protrusions for engaging a positioning upright wall for fitting the key groove and the engaging concave portions, are each provided.
Patent Document 1: Japanese Patent Application, Laid Open No. 2004-192967.
Patent Document 2: Japanese Utility Model Application, Laid Open No. Hei6-26179.
FIG. 8 is a plan view showing a configuration of FPCs and an FPC connector therefor, according to Patent Document 1. FIG. 8 of the present application corresponds to FIG. 1 of Patent Document 1. In FIG. 8, a first FPC 61 has a flat terminal 611, and a second FPC 62 has a second flat terminal 612.
Conductive patterns 613 and 614 formed of copper foil are exposed, respectively, on the back side of the flat terminals 611 and 612. The FPCs 61 and 62 each have four conductive wires (core wires). Furthermore, a first rectangular shaped protrusion 615 is formed on the right side of the first flat terminal 611, and a second rectangular shaped protrusion 616 is formed on the left side of the second flat terminal 612.
In FIG. 8, in cases in which the first conductive pattern 613 and the second conductive pattern 614 are each disposed on the back sides, the rectangular shaped protrusion 615 and the rectangular shaped protrusion 616 are disposed facing each other in the flat terminals 611 and 612.
In FIG. 8, an FPC connector 70 is composed of an insulating socket-housing 73 and an insulating cover-housing 74, with a plurality of C-shaped spring-contacts 75. A terminal socket 710, into which the flat terminals 611 and 612 are inserted, is formed in the socket-housing 73. Additionally, the plurality of C-shaped spring-contacts 75 is disposed in the socket-housing 73 so as to face the terminal socket 710.
The cover-housing 74 is rotatably coupled to the socket-housing 73 so as to open and close the terminal socket 710. In a state with the terminal socket 710 closed, the cover-housing 74 applies pressure to the plurality of C-shaped spring-contacts 75, to make them connect with the flat terminals 611 and 612 that are inserted into the terminal socket 710.
In a state with the cover-housing 74 of FIG. 8 opened, a central protrusion 730 is formed on the lower side of the terminal socket 710. On the bottom side of the terminal socket 710, a pair of upright walls 761 and 762 is formed so as to face the two flanks. At the front portion of the bottom face of the terminal socket 710, a notch 733 is formed, under which a protrusion 740, for preventing disconnection with respect to the cover-housing 74, is fitted.
In FIG. 8, the flat terminal 611 of the first FPC 61 is guided by a first side wall 731 of the central protrusion 730 and the upright wall 761, and is inserted into a first terminal socket 71a. Similarly, the flat terminal 612 of the second FPC 62 is guided by a second side wall 732 of the central protrusion 730 and the upright wall 762, and is inserted into a second terminal socket 71b. 
If the flat terminals 611 and 612 each advance a certain distance, the rectangular shaped protrusions 615 and 616 formed on the FPCs 61 and 62 make contact with the central protrusion 730, and the advance is halted. Next, when the cover-housing 74 is closed, the C-shaped spring-contacts 75 sandwich the flat terminals 611 and 612. Furthermore, when the cover-housing 74 is closed, the disconnection-prevention protrusion 740 fits under the notch 733.
In FIG. 8, if a force acts to separate the FPCs 61 and 62 from the connector 70, the rear edges of the rectangular shaped protrusions 615 and 616 each make contact with the disconnection-prevention protrusion 740, and the FPCs 61 and 62 are prevented from separating from the connector 70.
The FPCs shown in FIG. 8 are single-sided FPCs with a conductive pattern on one side only. Generally, copper foil is laminated on a base (also referred to as a base film) formed of polyimide or the like, and the copper foil is etched to form a conductive pattern. The conductive pattern is then coated with coverlay (also referred to as overlay) thin film, formed of polyimide or the like. In the terminal of a single-sided FPC connected to the connector, since the conductive pattern is exposed and a certain level of strength (rigidity) is required, a reinforcing plate formed of polyester or polyimide is affixed to the base.
On the other hand, in double-sided FPCs with conductive patterns on both sides of the base (insulating substrate), the terminal connected to the connector does not have a reinforcing plate. Additionally, in recent years, even for the single-sided FPC, in order to lower the profile of the connector, there is a tendency not to provide the reinforcing plate. For example, the profile of the mounting of the FPC connector is lowered to about 1 mm, and for the FPC connected to a connector with this type of low profile, the thickness of the terminal is decreased from 0.3 mm to about 0.15 mm.
With the FPCs shown in FIG. 8, very little force is required in inserting and disconnecting the FPCs, and it is what is called a ZIP (Zero Insertion Force) connector. In an FPC compatible with this ZIP-type FPC connector, in many cases, as in an FPC 81 described below in Patent Document 2, a pair of engaging convex portions is arranged on the two flanks of the connecting terminal, in order to prevent disconnection from the connector.
As described above, the FPCs with the pair of engaging convex portions arranged on the two flanks of the connecting terminals, for example, are latched by a pair of protrusions forming a pair of upright walls 761 and 762 (see FIG. 8), and the FPCs are prevented from disconnecting from the connector.
Furthermore, in the ZIF connector for the FPCs, in order to minimize the mounting area, there is a tendency to make the abovementioned pair of protrusions very small. Since this pair of protrusions is integrally formed with the housing from synthetic resin, when force tending to separate the FPCs from the connector acts, in a connector whose size has been minimized, the abovementioned pair of protrusions is easily broken by shearing force of the pair of engaging protrusions arranged in the FPCs.
In an FPC that is multi-polar with about 80 poles and has a narrow pitch of about 0.4 mm, with a thin film as described above, in order to prevent disconnection from the connector, for a connector compatible with an FPC in which a pair of engaging convex portions is provided, on the two flanks of a connecting terminal, a reinforced structure is required for a pair of protrusions that is latched by the abovementioned pair of engaging convex portions. This topic may be considered the object of the present invention.
FIG. 9 is a plan view of a partial transverse cross-section when the FPC and the connector, according to Patent Document 2, are connected. FIG. 9 of the present application corresponds to FIG. 3 of Patent Document 2. In FIG. 9, the FPC 81 is configured so that a plurality of conductive patterns 83 is disposed in parallel and separated, between upper and lower film 82 bands, the terminal of the single-sided film 82 is peeled for a prescribed length only, and the conductive patterns 83 are exposed, this being the connecting terminal 84.
Moreover, in the connecting terminal 84, a key groove 85 of approximately the same width as the conductive patterns 83, is formed in an asymmetric position in the width direction, opening to the front end 86. On the left and right side edges 87 of the longitudinal direction of the connecting terminal 84, in order to prevent disconnection from the connector, an engaging concave portion 88, a convex portion 89, and an insertion notch 810 are arranged, sequentially from the rear of the connecting terminal 84 towards the front edge 86.
Furthermore, corners of the insertion notch 810 and the front end 86 are cut to facilitate insertion of the connector. Additionally, an elongated hole 812 is provided near the convex area 89 in the connecting terminal 84, and elastic deformation is possible in inward and outward directions (in the direction of the width of the terminal 84) of the convex area 89.
Moreover, in FIG. 9, a slit 94, into which the connecting terminal 84 is inserted, is formed in the connector 93, into which the FPC 81 is inserted and is connected to. In the slit 94, a plurality of contacts 95, each separately electrically connected to the conductive patterns 83 of the connecting terminal 84, is housed in parallel. The contacts 95 are “swing-flex” type that sandwich and press-contact the connecting terminal 84.
Furthermore, inside the slit 94, a positioning upright wall portion 96 for fitting the key groove 85 is built at a position to accommodate the key groove 85. On the inner left and right side walls of the slit 94, an engaging protrusion 97 shaped so as to fit the engaging concave portion 88 is arranged jutting out.
In FIG. 9, when the FPC 81 is inserted into the slit 94 of the connector 93, the key groove 85 of the connecting terminal 84 fits the positioning upright wall 96 and is positioned, and the convex portion 89 of the connecting terminal 84 makes contact with the engaging protrusion 97 of the connector 93.
In addition, when the FPC 81 is inserted into the slit 94, the convex portion 89 elastically deforms in an inward direction with respect to the elongated hole 812 area, and after getting over the engaging protrusion 97, is restored, and the engaging concave portion 88 engages with the engaging protrusion 97 to prevent disconnection. At the same time, the plurality of conductive patterns 83 is electrically connected to the contacts 95. When the FPC 81 is removed, in the same way as for insertion, the convex portion 89 elastically deforms, so that easy removal from the connector 93 is possible.
The FPC connector shown in FIG. 9 is what is called a NON-ZIF connector. A low profile is possible with this type of NON-ZIF FPC connector; however, as described above, in a thin-film FPC that is multi-polar with about 80 poles, there is resistance to the plurality of contacts, and it is difficult to insert the FPC into the connector.
That is, although the connecting structure of the connector to the FPC shown in FIG. 9, having few poles, is effective with thick-film FPCs that have a reinforcing plate provided, application to a connecting structure for a connector to multi-polar, thin-film FPCs, which is an object of the present invention, is difficult. The addition of a slider to the terminal of an FPC and a mechanism for connecting this slider to the NON-ZIF FPC connectors has been invented; however, the slide thickness alone raises the mounting height of the connector, and this is not suited to the small and thin types of portable electronic devices of recent years. A new FPC connector that is suitable for ZIF FPC connectors and low profile connectors is required.